X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=README;h=074581cbe7cf8130d2d391cbbc85974e775d7b8f;hb=fe22a6565e85581207e3f4222eae26bc268223e4;hp=8dd7b5d74759860924adbc5b5fa70414af196113;hpb=cf46c3456f20acba34dd6543ea76de3b84b47401;p=perl%2Fmodules%2FScope-Upper.git diff --git a/README b/README index 8dd7b5d..074581c 100644 --- a/README +++ b/README @@ -2,7 +2,7 @@ NAME Scope::Upper - Act on upper scopes. VERSION - Version 0.06 + Version 0.10 SYNOPSIS package X; @@ -57,33 +57,39 @@ SYNOPSIS sub zap { try { return @things; # returns to try() and then outside zap() + # not reached } + # not reached } my @what = zap(); # @what contains @things DESCRIPTION - This module lets you defer actions that will take place when the control - flow returns into an upper scope. Currently, you can hook an upper scope - end, or localize variables, array/hash values or deletions of elements - in higher contexts. You can also return to an upper level and know which - context was in use then. + This module lets you defer actions *at run-time* that will take place + when the control flow returns into an upper scope. Currently, you can: + + * hook an upper scope end with "reap" ; + + * localize variables, array/hash values or deletions of elements in + higher contexts with respectively "localize", "localize_elem" and + "localize_delete" ; + + * return values immediately to an upper level with "unwind", and know + which context was in use then with "want_at". FUNCTIONS In all those functions, $context refers to the target scope. - You have to use one or a combination of "WORDS" to build the $context to - pass to these functions. This is needed in order to ensure that the - module still works when your program is ran in the debugger. Don't try - to use a raw value or things will get messy. - - The only thing you can assume is that it is an *absolute* indicator of - the frame. This means that you can safely store it at some point and use - it when needed, and it will still denote the original scope. + You have to use one or a combination of "WORDS" to build the $context + passed to these functions. This is needed in order to ensure that the + module still works when your program is ran in the debugger. The only + thing you can assume is that it is an *absolute* indicator of the frame, + which means that you can safely store it at some point and use it when + needed, and it will still denote the original scope. "reap $callback, $context" - Add a destructor that calls $callback when the upper scope represented - by $context ends. + Add a destructor that calls $callback (in void context) when the upper + scope represented by $context ends. "localize $what, $value, $context" A "local" delayed to the time of first return into the upper scope @@ -137,7 +143,9 @@ FUNCTIONS "unwind @values, $context" Returns @values *from* the context pointed by $context, i.e. from the - subroutine, eval or format just above $context. + subroutine, eval or format just above $context, and immediately restart + the program flow at this point - thus effectively returning to (or from, + depending on how you see it) an upper context. The upper context isn't coerced onto @values, which is hence always evaluated in list context. This means that @@ -145,6 +153,7 @@ FUNCTIONS my $num = sub { my @a = ('a' .. 'z'); unwind @a => HERE; + # not reached }->(); will set $num to 'z'. You can use "want_at" to handle these cases. @@ -158,9 +167,14 @@ FUNCTIONS my $num = sub { my @a = ('a' .. 'z'); unwind +(want_at(HERE) ? @a : scalar @a) => HERE; + # not reached }->(); - will righteously set $num to 26. + will rightfully set $num to 26. + +CONSTANTS + "SU_THREADSAFE" + True iff the module could have been built when thread-safety features. WORDS Constants @@ -178,10 +192,12 @@ WORDS The context of the scope just above $from. "SUB $from" - The context of the closest subroutine above $from. + The context of the closest subroutine above $from. Note that $from is + returned if it is already a subroutine context ; hence "SUB SUB == SUB". "EVAL $from" - The context of the closest eval above $from. + The context of the closest eval above $from. Note that $from is returned + if it is already an eval context ; hence "EVAL EVAL == EVAL". Getting a context from a level Here, $level should denote a number of scopes above the current one. @@ -197,11 +213,72 @@ WORDS e.g. "caller 0" refers to the caller context, "CALLER 0" will refer to the top scope in the current context. + Examples + Where "reap" fires depending on the $cxt : + + sub { + eval { + sub { + { + reap \&cleanup => $cxt; + ... + } # $cxt = SCOPE(0), or HERE + ... + }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0) + ... + }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + ... + }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + ... + + Where "localize", "localize_elem" and "localize_delete" act depending on + the $cxt : + + sub { + eval { + sub { + { + localize '$x' => 1 => $cxt; + # $cxt = SCOPE(0), or HERE + ... + } + # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0) + ... + }->(); + # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + ... + }; + # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + ... + }->(); + # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP + ... + + Where "unwind" and "want_at" point to depending on the $cxt: + + sub { + eval { + sub { + { + unwind @things => $cxt; + ... + } + ... + }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0) + ... + }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) + ... + }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2) + ... + EXPORT The functions "reap", "localize", "localize_elem", "localize_delete", "unwind" and "want_at" are only exported on request, either individually or by the tags ':funcs' and ':all'. + The constant "SU_THREADSAFE" is also only exported on request, + individually or by the tags ':consts' and ':all'. + Same goes for the words "TOP", "HERE", "UP", "SUB", "EVAL", "SCOPE" and "CALLER" that are only exported on request, individually or by the tags ':words' and ':all'. @@ -228,14 +305,16 @@ CAVEATS The first case is "solved" by moving the "local" before the "reap", and the second by using "localize" instead of "reap". - "reap", "localize" and "localize_elem" effects can't cross "BEGIN" - blocks, hence calling those functions in "import" is deemed to be - useless. This is an hopeless case because "BEGIN" blocks are executed + The effects of "reap", "localize" and "localize_elem" can't cross + "BEGIN" blocks, hence calling those functions in "import" is deemed to + be useless. This is an hopeless case because "BEGIN" blocks are executed once while localizing constructs should do their job at each run. + However, it's possible to hook the end of the current scope compilation + with B::Hooks::EndOfScope. Some rare oddities may still happen when running inside the debugger. It may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some - context fixes. + context-related fixes. DEPENDENCIES XSLoader (standard since perl 5.006). @@ -243,6 +322,11 @@ DEPENDENCIES SEE ALSO Alias, Hook::Scope, Scope::Guard, Guard. + Continuation::Escape is a thin wrapper around Scope::Upper that gives + you a continuation passing style interface to "unwind". It's easier to + use, but it requires you to have control over the scope where you want + to return. + AUTHOR Vincent Pit, "", . @@ -269,7 +353,7 @@ ACKNOWLEDGEMENTS Thanks to Shawn M. Moore for motivation. COPYRIGHT & LICENSE - Copyright 2008-2009 Vincent Pit, all rights reserved. + Copyright 2008,2009,2010 Vincent Pit, all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.